[PATCH] powerpc: Turn cpu_irq_down into kexec_cpu_down

We currently have a ppc_md member called cpu_irq_down, which disables IRQs
for the cpu in question. The only caller of cpu_irq_down is the kexec code.

On pSeries we need to do more than just teardown IRQs at kexec time, so rename
the ppc_md member to kexec_cpu_down and expand it. The pSeries code needs to
know, and other platforms might too, whether we're doing a crash shutdown (ie.
panicking) or a regular kexec, so add a flag for that.

The pSeries implementation of kexec_cpu_down does an unregister VPA call, which
tells the Hypervisor to stop writing stuff into our pacas. Without this we can
get weird memory corruption bugs when we kexec, caused by the Hypervisor
writing into the first kernel's pacas which happens to be somewhere interesting
in the second kernel's memory.

Signed-off-by: Michael Ellerman <[e-mail]>
Signed-off-by: Paul Mackerras <[e-mail]>

arch/powerpc/platforms/pseries/setup.c

···
 	if (ppc64_interrupt_controller == IC_OPEN_PIC) {
 		ppc_md.init_IRQ       = pSeries_init_mpic;
 		ppc_md.get_irq        = mpic_get_irq;
-	 	ppc_md.cpu_irq_down   = mpic_teardown_this_cpu;
 		/* Allocate the mpic now, so that find_and_init_phbs() can
 		 * fill the ISUs */
 		pSeries_setup_mpic();
 	} else {
 		ppc_md.init_IRQ       = xics_init_IRQ;
 		ppc_md.get_irq        = xics_get_irq;
-		ppc_md.cpu_irq_down   = xics_teardown_cpu;
 	}
 
 #ifdef CONFIG_SMP
···
 	return PCI_PROBE_NORMAL;
 }
 
+#ifdef CONFIG_KEXEC
+static void pseries_kexec_cpu_down(int crash_shutdown, int secondary)
+{
+	/* Don't risk a hypervisor call if we're crashing */
+	if (!crash_shutdown) {
+		unsigned long vpa = __pa(&get_paca()->lppaca);
+
+		if (unregister_vpa(hard_smp_processor_id(), vpa)) {
+			printk("VPA deregistration of cpu %u (hw_cpu_id %d) "
+					"failed\n", smp_processor_id(),
+					hard_smp_processor_id());
+		}
+	}
+
+	if (ppc64_interrupt_controller == IC_OPEN_PIC)
+		mpic_teardown_this_cpu(secondary);
+	else
+		xics_teardown_cpu(secondary);
+}
+#endif
+
 struct machdep_calls __initdata pSeries_md = {
 	.probe			= pSeries_probe,
 	.setup_arch		= pSeries_setup_arch,
···
 	.check_legacy_ioport	= pSeries_check_legacy_ioport,
 	.system_reset_exception = pSeries_system_reset_exception,
 	.machine_check_exception = pSeries_machine_check_exception,
+#ifdef CONFIG_KEXEC
+	.kexec_cpu_down		= pseries_kexec_cpu_down,
+#endif
 };

arch/ppc64/kernel/machine_kexec.c

···
  */
 void kexec_smp_down(void *arg)
 {
-	if (ppc_md.cpu_irq_down)
-		ppc_md.cpu_irq_down(1);
+	if (ppc_md.kexec_cpu_down)
+		ppc_md.kexec_cpu_down(0, 1);
 
 	local_irq_disable();
 	kexec_smp_wait();
···
 	}
 
 	/* after we tell the others to go down */
-	if (ppc_md.cpu_irq_down)
-		ppc_md.cpu_irq_down(0);
+	if (ppc_md.kexec_cpu_down)
+		ppc_md.kexec_cpu_down(0, 0);
 
 	put_cpu();
 
···
 	 * UP to an SMP kernel.
 	 */
 	smp_release_cpus();
-	if (ppc_md.cpu_irq_down)
-		ppc_md.cpu_irq_down(0);
+	if (ppc_md.kexec_cpu_down)
+		ppc_md.kexec_cpu_down(0, 0);
 	local_irq_disable();
 }
 

include/asm-powerpc/machdep.h

···
 
 	void		(*init_IRQ)(void);
 	int		(*get_irq)(struct pt_regs *);
-	void		(*cpu_irq_down)(int secondary);
+#ifdef CONFIG_KEXEC
+	void		(*kexec_cpu_down)(int crash_shutdown, int secondary);
+#endif
 
 	/* PCI stuff */
 	/* Called after scanning the bus, before allocating resources */